Endothelial Function in Lower Extremity Bypass Grafts

This study will determine whether or not saphenous vein [arterial] bypass grafts in the leg relax in response to increases in blood flow.

Subjects who have undergone saphenous vein [arterial] bypass grafts from the femoral to above-knee popliteal artery will undergo ultrasound imaging at rest, and again after 5 minutes of blood pressure cuff occlusion of the calf. (at 1 minute and 15 minutes) Subjects will then be given sub-lingual nitroglycerin, and repeat ultrasound will be performed 3 minutes later. Following 10 minutes of rest, subjects will be given intravenous L-NMMA, a specific nitric oxide inhibitor, to help determine the responsible agent of the vein graft flow mediated dilation.

Investigators who analyzed the results of vascular function testing were blinded to the participant identity.

ultrasound imaging of saphenous vein bypass graft following an ischemic stimulus, administration of sublingual nitroglycerin and intravenous administration of L-NMMA.

L-NMMA was infused at a dose of 1 mg/kg over 10 minutes to competitively inhibit the production of nitric oxide. Ultrasound imaging of the saphenous vein [arterial] bypass at baseline, and following an ischemic stimulus, administration of sublingual nitroglycerin, and intravenous administration of L-NMMA.

Flow-mediated, endothelium-dependent vasodilation was determined by comparing baseline vein graft diameter with vein graft diameter as measured after deflation of a 2.5-inch wide sphygmomanometric cuff that had been inflated to suprasystolic pressure for 5 minutes. The cuff was never placed directly over the graft. Vasodilation of the vein graft was determined by acquiring images at 1 minute after cuff deflation.

Inclusion Criteria: Adults who have undergone femoral artery to above-knee popliteal artery saphenous vein bypass grafts Exclusion Criteria: Amputation beyond the toes Critical limb ischemia defined as rest pain, non-healing ulceration or gangrene Pregnancy